 |
|
| Dick Gray, founder of the Freshwater Society, has written the Passwords column since 1968. The columns are based on Gray’s belief that we must use our vast knowledge to work toward the preservation of water. |
The “final completion” of the gigantic Three Gorges Dam on China’s Yangtze River in May 2011 was supposed to be greeted by cheers and congratulations for all involved. But there have been two “completions” to date with many major drawbacks uncovered as the dam neared what was supposed to be its victorious end.
One completion was construction of the dam. A second completion was the certification for operation of the gigantic turbines driven by impounded water.
Now, a third “completion” will occur in a couple of years, after workers to try to clean up a mess of problems that had been foreseen by some, but dismissed by most.
It’s no wonder there are still problems. The dam has a face with a height of 594 feet, a length of a mile and a half and an operating bank of up to 34 giant turbines, each weighing 6,000 tons and revolving at 75 rpm. The turbines are powered by a vast lake of water 600 feet deep in spots and stretching 410 miles in length.
Dams – especially high dams of 50 ft or more – are notorious for flaws in the structure, negative impacts on displaced persons, the loss of antiquities and the flooding of geological treasures.
Yet dams – especially high dams – bring a variety of benefits to their territory and its people. These dams accumulate water for irrigation, aid in flood control and provide recreation and other services for humans. However, the most important use of high dam water is to make electricity.
A dam at the site of the Three Gorges was conceived in 1919 by Sun Yat-Sen, but controversy, politics, revolution and design disagreements delayed a serious consideration of such a mammoth project until the National People’s Congress approved a final plan in 1992. At a recent dedication ceremony, Chinese Premier Wen Jiabau and President Hu Jintao, trained in geological and hydraulic engineering, failed to appear “because as industry insiders they were aware of the risks of the project.” That is a quote from environmental activist Dai Qing, who opposed the Three Gorges dam.
During this extended construction period, severe problems were encountered and some may never be corrected.
There are high dams and low dams and temporary dams. The magazine “Outside” reports there are 47,655 large dams at least 100 feet tall in 140 countries. A Swedish hydrologist states there are 45,000 dams more than 46 feet tall. Who to believe? There is no doubt there are many, many dams in existence today and all of them have finite lifespans.
James Syvitski of the University of Colorado in Boulder states there is ONE LARGE DAM being started or completed EVERY DAY some place in the world, a pace that will continue for ONE HUNDRED YEARS.
Today, the Three Gorges dam makes the news for being a big deal and big it is.
It is 50 times larger than the large Fort Peck dam in Montana, and who knows what the limit will be for large dams in the world.
Today, the second-largest dam in the world is in Canada and has been built from tailings from the oil sands extractions.
As a general rule, there are five types of high dams:
• Earthen Dams – Both impervious and pervious.
• Rock-fill Dams – Made of loose rocks and boulders.
• Solid Concrete – Hoover and the Three Gorges dams are examples.
• Hollow Gravity Buttresses Dams – Buttresses on the downstream side save concrete and result in a dam that can be enlarged.
Dams have Finite lives – but then, nothing is forever. Yet dams are a special case. As water accumulated behind a dam, its flow becomes nil and suspended material settles out and eventually displaces impounded water with sediments. Then what? In time, high hopes turn into mountains of crud and toxic material.
A recent report on U.S. dams by the American Society of Civil Engineers said there are some 85,000 dams in this country, and only 11 percent of those are owned or regulated by the federal government. The report said state dam inspection programs are often inadequate, and sometimes nonexistent.
The report estimated there are more than 4,000 unsafe or deficient dams in the U.S.
It’s a basic no-win situation. And we’re compounding the problems by building more dams, high and low, with high hopes, knowing future generations will have to pay the price.